The present invention relates in general to tightening devices for use in bolt-and-nut fastenings and, more particularly, to a torque tool.
Known prior art torque tools, either of the general category of this invention or having specific features of interest, are found in a great number among the U.S. patents. However, several design problems, which directly influence the reliability and service life of these tools, are not addressed.
It is a first objective of this invention to design sun gears integrally with one of the disc-shaped plates of planet carrier cages, by this preventing misalignment of the main components and reducing the manufacturing costs.
It is a second objective of this invention to enhance the service life of an important subassembly of the torque tool the stepped pin-subassembly, by using, there where the velocity is higher, a larger diameter bearing.
It is the third objective of the present invention: to use roll needles characterized by a high strength and wear resistance, thus allowing the tool to operate normally for a longer period of time.
The torque tool, conform the present invention, comprises a torque converter actuated by a motor. The torque converter includes a housing incorporating internally, with sequentially decreasing diameters, the following: a threaded bore, an annular indentation, an internal spur gear and a smooth bore; and externally, an external spur or a hexagonal zone. The torque converter further comprises a flange for interconnecting the torque converter with the motor. The torque converter incorporates as well a threaded ring for engaging the threaded bore. The threaded ring is mounted with a close-running feet to a cylindrical extension of the flange and with a sliding contact to a flat surface of the flange. The threaded ring is provided with several axially through-holes circumferentially and equidistantly disposed with respect to the axis of the threaded ring. An index plate, located in the annular indentation, comprises a multiplicity of orifices disposed on a circumference equal to that of the several axially through-holes. Several resiliently biased balls are essentially disposed in the through-holes and partially in a corresponding number of orifices of the multiplicity of orifices. Use is made of fasteners for securing the index plate against the flange.
The torque converter further comprises an input shaft assembly incorporating a first sun gear, centrally provided with a blind hole, a first needle bearing inserted with a close-fit in the blind hole and a first bearing for holding the input shaft against the flange. In the torque converter there is a first planet carrier assembly, which includes first and second disc-shaped plates, equally spaced and firmly interconnected. The first disc-shaped plate is provided with a centrally located, axial passage for the first sun gear. The second disc-shaped plate is centrally provided with an outwardly extending second sun gear. The former and the latter form a unitary structure having a central through-opening wherein a first sliding bearing is press-fitted. A first planetary gear is encased in the first planetary carrier. This first planetary gear comprises, besides the first sun gear, three first planet pinions drivingly engaged with the first sun gear and the internal spur gear. The torque converter further comprises a second planet carrier comprising a third and a fourth disc-shaped plates, equally spaced and firmly interconnected. The third disc-shaped plate is provided with a central access opening for the passage of the second sun gear. The fourth disc-shaped plate is provided with an outwardly extending third sun gear, with which it forms a unitary structure having a central through opening into which a second sliding bearing is press-fitted. The second sliding bearing is coaxial with and has an internal diameter equal to the first sliding bearing. The second planetary gear is encased in the second planet carrier and comprises, besides the sun gear, three-second planet pinions drivingly engaged with the second sun gear and internal spur gear. The torque converter incorporates as well a third planet carrier having a fifth and a sixth disc-shaped plate equally spaced and firmly interconnected. The fifth disc-shaped plate, which is directed towards the second planet carrier, is provided with a third central access opening for the passage of the third sun gear. The sixth disc-shaped plate has an outwardly extending hub, successively followed by a fourth sun gear, and a bearing journal. The external diameters of the hub, fourth sun gear and bearing journal diminish consecutively. The sixth disc-shaped plate together with the hub, the first sun gear and the bearing journal constitute a unitary structure. A third sliding bearing is press fitted in a central closed hole located in the sixth disc-shaped plate and the hub. The third sliding bearing is coaxial with and has the same diameter as the second sliding bearing. A third planetary gear is disposed in the third planet carrier and includes, besides the third sun gear, three third planet pinions and, finally, needles to support the third planet pinions on axles. The axles are firmly secured to the fifth and sixth disc-shaped plates. The third planet pinions are drivingly engaged with the third sun gear and the internal spur gear. A stepped pin for preventing misalignment of first, second and third planetary gears is inserted into the first, second and third sliding bearings.
The torque converter further comprises a fourth planet carrier. The latter includes a seventh and an eighth disc-shaped plates, equally spaced and firmly interconnected by attaching elements. The seventh disc-shaped plate is provided with a centrally located cylindrical sleeve. A second bearing is inserted so it has its inner race light-press fitted onto the cylindrical sleeve and its outer race mounted with an interference fit against the internal spur gear. The internal diameter of the cylindrical sleeve is commensurate, with the outwardly extending hub, to allow a free passage of the latter. The eighth disc-shaped plate extends concentrically with a hub of reduced diameter and ends with an output shaft, having a reduced diameter with respect to the concentrical hub. The eighth disc-shaped plate together with the concentrical hub and the output shaft form a unitary structure. A fourth sliding bearing is press fitted in a blind hole formed in the eighth disc-shaped plate and partially in the concentrical hub. The fourth sliding bearing is coaxial with and has the same diameter as the bearing journal. A fourth planetary gear is encased in the fourth planet carrier and includes, besides the fourth sun gear, four fourth planet pinions. A multiplicity of roll needles, which are closely spaced together between each one of the fourth planet pinions and each one of the axles, is inserted. The fourth planet pinions are drivingly engaged with the fourth sun gear and the internal spur gear. Finally, a hub bearing is located between the hub and the smooth bore.
In one aspect of the invention, the stepped pin has a larger diameter corresponding to the internal diameter of the first needle bearing and the small diameter commensurate with the lady internal diameter of the first, second and third sliding bearings. In another aspect of the invention, the multiplicity of roll needles, which are closely spaced together, is inserted between the planet pinions and the axles. The material used for the axles is VascoMax Steel C-350 (trade name). Broadly stating, the torque tool comprises a torque converter which includes:
at least three planet carriers; and
at least three planetary gears encased in the three planet carriers; and each of the three planetary gears includes a sun gear and at least three planet pinions. Each of the three planet carriers has an input disc-shaped plate, directed towards an input shaft and an output disc-shaped plate directed towards an output shaft, both input and output shafts being the main shafts of the torque tool. Two of the at least three planet carriers which are next to the input shaft have their output disc-shaped plates extending into sun gears with which they form a unitary structure.